Google had 65.7 percent of searches last month, an increase from 65.4 percent in February, Heath Terry, an analyst at Canaccord Genuity in New York, wrote in a note, citing data from Reston, Virginia-based ComScore. Microsoft’s Bing search engine had 13.9 percent, up from 13.6 percent. Yahoo’s share slipped to 15.7 percent, from 16.1 percent.

Google, which gets most of its revenue from search-based advertising, has been trying to improve the relevance of results with updates and new features. In February, the company changed the way it carries out Web searches to feature more “high-quality” sites, affecting 12 percent of queries.

Last month, the company announced features to make the query results and related advertising more social, letting users tell their friends whether they like a search result.

Google, based in Mountain View, California, fell $6.76 to $570.61 yesterday on the Nasdaq Stock Market. The shares have declined 3.9 percent this year.